Dark Worlds
The sixth episode of Mesozoic Earth. It focuses on the caves and sinkholes of the Mesozoic. Animals featured *''Anurognathus'' *''Nothosaurus'' *''Cave Labyrinthodont'' *''Cave Lungfish'' *Postosuchus *Cave Crab *Cave Sponge *Giant Glowworms *The Mogollon Monster (heard only) *''Pannoniasaurus inexpectatus speluncus'' *''Pteranodon sternbergi'' Plot Sequence One We are up in the higher parts of Canada, the late Cretaceous. A vast glacier stands in the way. The entrance of massive cave stands. We go into it. At first, it is wide. The surface of the ceiling is all glacial ice. Sometimes, ice caves form in the glaciers, and they can reach incredibly depths. It is winter, so meltwater doesn't run from the cave. As we go deeper, the incredibly wide cave, becomes smaller, and smaller, and the roof is getting lower and lower, to the point, that you'd have to crawl to get around. But, it soon gets too low. But the sight on the other side, is worth it. Once you reach the outside, a massive room of ice, with what appear to be bubbles in it, stretches out for miles. Icicles hang out. How did something like this form? The answer, is underground. Hot springs underneath warm and help melt the ice, creating this cave. How the bubble ice room is created, however, is not known. This is the way these caves are, but for the rest of the world's cave, they are made in much different ways, and are not made of glacial ice. Sequence Two Sequence Three Sometimes, erosion occurs under ground. In a massive sinkhole, in the Switzerland forests of the Carnian, a massive waterfall flows down. That water flows down into tunnels of rivers. This constant motion of water eroding limestone, makes the water slightly acidic, and create these tunnels. They are beginnings of rivers. One day, they will emerge out of another cave entrance, and a new river will be born. Sequence Four In the inland Switzerland forests, a cenote lies. It supports live from miles around. Underwater, a bustling community of fish live, feeding on the thick carpets of algae here. But down below, the true extent of the cenote, is breathtaking. The roots of the trees are visible down here. The water here helps the roots grow, and the tree to grow. But beyond, is a vast network of caverns, and beautiful stalactites and stalagmites hang and project from the rocks. We enter an area of what looks like air. But in fact, it is just water. We have traveled for miles. This thick cloudy water is created by the meeting of freshwater, and the meeting of saltwater. Somewhere, is the ocean. All cenotes here flood out to the ocean. We get to the other side, the ocean entrance to the cenote. Fish are in abundance. But feeding on the fish, are Nothosaurus. They are like seals, and are highly active. They catch a few and eat both underwater, and above at the surface. Nothosaurus are giganotherms, creating body heat by remaining highly active. They are curious, and the entrance to the cenote is enticing. They take a deep breathe and enter the cave. They swim in, but then spot a squeeze, a very thin area between the ocean cave, and the rest of the cenote. But nothosaurs are notoriously curious, and push through the squeeze. They exit out, and swim around. It is totally dark, but their large eyes help pick out any fish here. They can only stay so long. It is time to breathe. The nothosaurs push through the squeeze, and barely make it to the surface to breathe in time. Sequence Five Outside the river landscape of Siberia, in the Middle Triassic. There is an entrance to a cave. There, a community of animals, troglobites, live, ones who never come out, and never see light, in their lives. They are the most extreme of all animals. In the clear pools of this Siberian cave, blind fish feed on the bacteria growing along the sides of the limestone. One main pool, is the largest of all, as big as a lake. They hold the strangest Triassic amphibian. Swimming up for a breath, is a cave labyrinthodont. This amphibian is only a metre long, but is very bizarre. He has no eyes. He doesn't need them. He is related to the Siderops in Australia, and look similar. In addition to being blind, he has no pigment in his skin, he is colourless. His skin can detect the slightest movement in the water. He swims to the bottom, only ten metres down, and waits. A fish swims by. Then, he lunges and catches it. The labyrinthodont is extremely rare, and extremely specialized. It only feeds on one particular species of cave fish, and inhabit only this lake. But the numbers are dropping rapidly. Each year, as the pool is being drained by the formation of a stream, fewer, and fewer cave labyrinthodonts live. There is only twenty five of them left in the wild, and they only live in this cave, and only in this "lake". Sequence Six The dry deserts of the Mongollon. We are in the late Triassic. By now, the cave labyrinthodonts have been long, long gone. This area experiences extreme droughts. Sometimes, not a single drop of water, or even moisture drops on the desert in one year. Animals have to adapt to these most harshest of conditions. A lone Postosuchus is looking for water. Being a mesotherm, he can go longer without water than most animals. But the desert Postosuchus are very rare, only 100 live in the wild today. This, is an extremely rare sight. He has smelt water. He approaches a cliff edge and looks down. There is water at the entrance of a massive cave. The problem is, from both sides, there are cliffs, 40 metres high. No animal except insects can reach them. This cave is the most interesting of caves, as it holds the largest underground lake of all time. Even the Dragon's Breath Cave in Africa, is minute compared to this one. Troglobites of some kind live here. The depth of this lake, is almost as deep as some parts of the ocean. And swimming are a few giant, 2 metre long lungfish, who resemble golden cave catfish. The depth is almost too deep for the mind to comprehend. Freshwater crabs live here. This lake is so big, that there are mysteries of what other animals live here. Occasionally, the lungfish surface, but are dead, bitten in half or torn apart. So far, there hasn't been a single candidate for this bizarre string of deaths. The crabs are predatory, but they don't scavenge, and only feed on the small fish here. The lungfish are very tranquil, and feed only on algae, and are not capable of this horrendous act. The lungfish are the largest animals found here, but this act means that a far bigger animal is here, one that is predatory. What that could be is anyones guess, but one thing's for sure; there is something scary in this deep lake. But there is another mystery, possibly connected to the dead lungfish. There is very loud, infrasonic sounds filling the water. It sounds like it is echoing, so it is difficult to pinpoint the location of the sound. However, it is clearly from an animal, and a big one. The only vertebrates here are fish, and they can't make this noise. It is entirely possible that the same animal who has killed the lungfish is making these noises. The depth of this lake means that the mystery animal lives in the deeper parts, that have not been mapped. The lake also has very bizarre sponges, adapted to the low light conditions. Another infrasonic song fills the water. It is very loud. Further into the cave, the ceiling above the water is littered with very big glowing blue lights. It looks like a galaxy; a galaxy of giant glowworms. These are only larvae, and they hang against the ceiling with a series of sticky hammocks. With the higher oxygen content, these worms grow up to a foot long. They hang sticky strings, then light their ends to attract insects. And it works. A dragonfly gets stuck in a string, and it reels in its catch. This lake is considered, the most interesting of lakes. How it was formed, is a mystery. Sequence Seven Sequence Eight Trivia *The first and third sequences feature no animals. *The first sequence focuses on an ice cave.